The invention is generally directed to toner and developer compositions, and more specifically, the present invention is directed to developer and toner compositions containing charge enhancing additives, which impart or assist in imparting a negative charge to the toner particles and enable toners with rapid triboelectric charging characteristics. In embodiments, there are provided in accordance with the present invention toner compositions comprised of toner resins, pigment particles or dye molecules, and certain aluminum complex charge enhancing additives. In another embodiment, the present invention is directed to toners with aluminum complex charge enhancing additives, which additives can be obtained, for example, from the reaction of aluminum ion with two molar equivalents of ortho-hydroxybenzoic acid and an ortho-hydroxyphenol in the presence of an appropriate base such as potassium hydroxide or an amine. The aforementioned charge additives in embodiments of the present invention enable, for example, toners with rapid triboelectric charging characteristics, extended developer life, stable triboelectrical properties irrespective of changes in environmental conditions, and high image print quality with substantially no background deposits. Also, the aforementioned toner compositions usually contain a colorant component comprised of, for example, color pigments or dyes such as black, cyan, magenta, yellow, blue, green, red, or brown color, or mixtures thereof thereby providing for the development and generation of black and/or colored images. The toner and developer compositions of the present invention can be selected for electrophotographic, especially xerographic, imaging and printing processes, including color processes.
Toners with negative charge enhancing additives are known, reference for example U.S. Pat. Nos. 4,411,974 and 4,206,064, the disclosures of which are totally incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of toner resins, pigment particles, and as a charge enhancing additive ortho-halophenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additives. In U.S. Pat. No. 4,845,003 there are illustrated negatively charged toners with certain aluminum salt charge additives. More specifically, this patent discloses as charge additives aluminum complexes comprising of two or three hydroxybenzoic acid ligands bonded to a central aluminum ion. While these charge additives may have the capability of imparting negative triboelectric charge to toner particles, they are generally not efficient in promoting the rate of triboelectric charging of toner particles. A fast rate of triboelectric charging is particularly crucial for high speed xerographic machines since, for example, these machines consume toner rapidly, and fresh toner has to be constantly added. The added uncharged toners, therefore, must charge up to their equilibrium triboelectric charge level rapidly to ensure no interruption in the xerographic imaging or printing operation. Another shortcoming of these charge additives is their thermal instability, that is they often break down during the thermal extrusion process of the toner manufacturing cycle. Most or many of these and other disadvantages are eliminated, or substantially eliminated with the metal complex charge additives of the present invention.
Developer compositions with charge enhancing additives, which impart a positive charge to the toner particles, are also well known. Thus, for example, there is described in U.S. Pat. No. 3,893,935 the use of quaternary ammonium salts as charge control agents for electrostatic toner compositions; U.S. Pat. No. 4,221,856 which discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R radicals are hydrocarbons having from 8 to about 22 carbon atoms, and each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens such as iodide, chloride and bromide, reference the Abstract of the Disclosure and column 3; a similar teaching is presented in U.S. Pat. No. 4,312,933 which is a division of U.S. Pat. No. 4,291,111; similar teachings are presented in U.S. Pat. No. 4,291,112 wherein A is an anion including, for example, sulfate, sulfonate, nitrate, borate, chlorate, and the halogens; U.S. Pat. No. 4,338,390, the disclosure of which is totally incorporated herein by reference, illustrates developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition; and U.S. Pat. No. 4,298,672, the disclosure of which is totally incorporated herein by reference, illustrates positively charged toner compositions with resins and pigment particles, and as charge enhancing additives alkyl pyridinium compounds.
Illustrated in copending patent applications U.S. Ser. No. 047,902 is a negatively charged toner composition comprised of resin, pigment or dye particles, optional surface additives, and an aluminum complex composite charge additive containing active charge enhancing components as represented by the following formulas ##STR1## wherein R is a hydrogen, halogen, alkyl, aryl, alkoxy, aryloxy, hydroxy, nitro, or an amino substituent; Ar represent an aromatic group; M.sup.+ is a proton, an alkaline metal cation, or an ammonium ion; and m is a number of from 1 to about 3; and in U.S. Ser. No. 047,903 is a negatively charged toner composition comprised of resin or resins, pigment particles, optional surface additives, and an aluminum charge enhancing additive represented by the following formula ##STR2## wherein R and R' are independently selected from the group consisting of hydrogen, alkyl, aryl, alkoxy, aryloxy, hydroxy, halogen, amino, cyano, and nitro; R" is hydrogen or hydroxy; M.sup.+ is a counter cation comprised of a proton, an ammonium ion, a substituted ammonium ion or a metal cation; and x and y are the numbers 1 or 2, the disclosures of which are totally incorporated herein by reference.
In copending applications U.S. Ser. No. 978,572 is a negatively charged toner composition comprised of resin particles, pigment particles, optional surface additives, and a halogenated salicyclic acid complex charge enhancing additive of the following formula ##STR3## wherein Z is zinc or chromium; M is hydrogen, an alkali metal, an alkaline earth metal, NH.sub.4, or NR.sub.4 wherein R is alkyl; X and Y are independently selected from the group consisting of chloride, iodide and bromide; and n and m are the numbers 1 or 2; in U.S. Ser. No. 978,584 is a negatively charged toner composition comprised of resin particles, pigment particles, optional surface additives, and a halogenated salicylic acid charge enhancing additive of the following formula ##STR4## wherein X is halogen, M is hydrogen, an alkaline earth, an alkali metal, or NR.sub.4 wherein R is alkyl, and n is the number 1 or 2; and in U.S. Ser. No. 978,571 is a negatively charged toner composition comprised of resin particles, pigment particles, optional surface additives, and a halogenated aluminum salicylic acid complex charge enhancing additive of the following formulas ##STR5## wherein M is hydrogen, an alkali metal, an alkaline earth metal, NH.sub.4, or NR.sub.4 wherein R is alkyl; X and Y are independently selected from the group consisting of iodide, chloride and bromide, and n and m are the numbers 1 or 2, the disclosures of which are totally incorporated herein by reference.
Although many charge enhancing additives are known, there continues to be a need for charge enhancing additives which provide toners with many of the advantages illustrated herein. There is also a need for negative charge enhancing additives which are useful for incorporation into black and colored toner compositions which can be utilized for developing positive electrostatic latent images. Moreover, there is a need for colored toner compositions containing charge enhancing additives which do not interfere with the color quality of the colorants present in the toners. Another need relates to the provision of toner compositions with certain charge enhancing additives, which toners in embodiments thereof possess substantially stable triboelectric charge levels, and display acceptable rates of triboelectric charging characteristics. Furthermore, there is also a need for toner compositions with certain charge enhancing additives based on hybrid aluminum complexes with both salicylate and catechol ligands, which possess excellent dispersibility characteristics in toner resins, and can, therefore, form stable dispersions in the toner compositions. There is also a need for negatively charged black and colored toner compositions that are useful for incorporation into various imaging processes, inclusive of color xerography, as illustrated in U.S. Pat. No. 4,078,929, the disclosure of which is totally incorporated herein by reference; laser printers; and additionally a need for toner compositions useful in imaging apparatuses having incorporated therein layered photoresponsive imaging members, such as the members illustrated in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Also, there is a need for negative toner compositions which have desirable triboelectric charge levels of, for example, from between about -10 to about -40 microcoulombs per gram, and triboelectric charging rates of less than about 120 seconds, and preferably from about 15 to about 60 seconds as measured by standard charge spectrograph methods when the toners are frictionally charged against suitable carrier particles via roll milling. There is also a need for nontoxic, substantially nontoxic, or environmentally compatible charge enhancing additives, which when incorporated at effective concentrations of, for example, less than 7 weight percent, preferably less than 5 weight percent in toners, render the toners to be environmentally friendly. An additional need resides in the provision of simple and cost-effective preparative processes for the aluminum complex charge enhancing additives of the present invention. The concentrations of the charge additives that can be incorporated into the toner compositions generally range from about 0.05 weight percent to about 5 weight percent, depending on whether the charge additive is utilized as a surface additive or as a dispersion in the bulk of the toner. The effective concentrations of toner in the developer, that is toner and carrier particles, are, for example, from about 0.5 to about 5 weight percent, preferably from about 1 to about 3 weight percent.